The Lincoln index is used to estimate the size of a population based on the number of marked
individuals recaptured after an initial group of a species was captured, marked and released. The
equation is given below:
𝑁=
𝑀×𝑛
𝑚
M = number of individuals caught, marked and released
n = number of individuals caught on second sampling
m = number of individuals recaptured that were marked
Below is data from a study on sharks
No. marked and
No. captured (2nd
No. marked (2nd
Estimated
released (1st visit)
visit)
visit)
population size
0
83
58
12
1
64
52
14
2
57
50
15
3
52
43
22
4
45
55
32
5
33
48
22
6
28
30
19
7
22
17
10
8
9
7
5
9
0
0
0
Shark age (years)
1. Complete the table above by filling in the right-hand column. Show your working out to the
first two rows.
2. State 2 limitations to this study and explain the impact they may have on this data.
3. Graph the data on the grid below
4. What are the four factors that affect changes in population?
5. Predict 2 causes of the population decline in these sharks